Cancer is the second leading cause of death in the United States, after heart disease (Boring et al., CA Cancer J. Clin., 43:7 (1993)), and develops in one in three Americans. One of every four Americans dies of cancer. Cancer is characterized primarily by an increase in the number of abnormal, or neoplastic, cells derived from a given normal tissue which proliferate to form a tumor mass, the invasion of adjacent tissues by these neoplastic tumor cells, and the generation of malignant cells which spread via the blood or lymphatic system to regional lymph nodes and to distant sites. The latter progression to malignancy is referred to as metastasis.
Cancer can be viewed as a breakdown in the communication between tumor cells and their environment, including their normal neighboring cells. Signals, both growth-stimulatory and growth-inhibitory, are routinely exchanged between cells within a tissue. Normally, cells do not divide in the absence of stimulatory signals, and likewise, will cease dividing in the presence of inhibitory signals. In a cancerous, or neoplastic, state, a cell acquires the ability to “override” these signals and to proliferate under conditions in which normal cells would not grow.
Tumor cells must acquire a number of distinct aberrant traits to proliferate. Reflecting this requirement is the fact that the genomes of certain well-studied tumors carry several different independently altered genes, including activated oncogenes and inactivated tumor suppressor genes. Each of these genetic changes appears to be responsible for imparting some of the traits that, in aggregate, represent the full neoplastic phenotype (Land et al., Science, 222:771 (1983); Ruley, H. E., Nature 304:602 (1983); Hunter, T., Cell, 64:249 (1991)).
In addition to unhindered cell proliferation, cells must acquire several traits for tumor progression to occur. For example, early on in tumor progression, cells must evade the host immune system. Further, as tumor mass increases, the tumor must acquire vasculature to supply nourishment and remove metabolic waste. Additionally, cells must acquire an ability to invade adjacent tissue, and, ultimately, cells often acquire the capacity to metastasize to distant sites.
A variety of biochemical factors have been associated with different phases of metastases. Cell surface receptors for collagen, glycoproteins such as laminin, or proteoglycans facilitate tumor cell attachment, an important step in invasion and metastases. Attachment then triggers the release of degradative enzymes which facilitate the penetration of tumor cells through tissue barriers. Once the tumor cells have entered the target tissue, specific growth factors are required for further proliferation.
One of the major characteristics of cancer cells is their ability to invade surrounding normal tissues and metastasize to distant body sites. It is the metastatic nature of malignant tumors that presents a great challenge to clinicians in terms of treatment, since the tumor is no longer localized to one area.
Tumor invasion (or progression) is a complex series of events, in which tumor cells detach from the primary tumor, break down the normal tissue surrounding it, and migrate into a blood or lymphatic vessel to be carried to a distant site. The breaking down of normal tissue barriers is accomplished by the elaboration of specific enzymes that degrade the proteins of the extracellular matrix that make up basement membranes and stromal components of tissues.
Elevated proteolytic activity has been implicated in neoplastic progression. The role(s) of proteolytic enzymes, including serine proteases, in neoplastic progression are under study. Proteases have been proposed to contribute to the degradation of excellular matrix and to tissue remodeling and, thus, may assist in cancer invasion and metastasis.
A number of extracellular proteases have been reported and expression of some of these proteases has been said to correlate with tumor progression. (Mignatti et al., Physiol. Rev., 73:161-195 (1993).)
A class of extracellular matrix degrading enzymes has been identified called the matrix metalloproteinases (MMPs). Two of the matrix metalloproteinases have been implicated in tumor invasion. The type IV collagenase has been correlated with the metastatic potential of tumor cells. (Liotta et al., Nature, 284:67-68 (1980)). It has been reported that the production of the matrix metalloproteinase stromelysin was associated with malignant tumors with metastatic potential. (McDonnell and Matrisian, Smnrs. in Cancer Biology, 1:107-115 (1990); McDonnell and Matrisian, Cancer and Metastasis Reviews, 9:309-319 (1990).)
The capacity of cancer cells to metastasize and invade tissue has been reported to be facilitated by degradation of the basement membrane. Several proteinase enzymes have been reported to facilitate the process of invasion of tumor cells. One family of enzymes, the MMPs, has been implicated as enhancing degradation of the basement membrane to allow tumorous cells to invade tissues. MMPs have been reported to differ in molecular weight and antigenic properties. Previously, two major metalloproteinases having molecular weights of about 70 kDa and 92 kDa have been studied. Both of these MMPs have been reported to enhance ability of tumor cells to metastasize. Two natural inhibitors of these enzymes known as tissue inhibitors of metalloproteinase (TIMP) have been identified. The inactivated unclipped collagenases are generally secreted as a complex with TIMP. Enzymatic activity of the 70 kDa and 92 kDa proteins has been reported to depend on secreted ratios of collagenase/TIMP.
Matriptase is a trypsin-like serine protease has also been isolated and cloned from T-47D human breast cancer cells. Matriptase has been isolated from T-47D cell-conditioned medium. (Lin et al., J. Biol. Chem., 274(26):18231-18236 (1999).) Upon analysis of the cDNA, it was determined that the protease had 683 amino acids and contained three main structural regions: a serine protease domain near the carboxyl-terminal region, four tandem low-density lipoprotein receptor domains, and two tandem complement subcomponents, C1r and C1s. Matriptase was reported to be a mosaic protein with broad spectrum cleavage activity and two potential regulatory modules. It was named “matriptase” because of the ability of the protease to degrade the extra-cellular matrix and its trypsin-like activity. (Lin et al., J. Bio. Chem., 274:18231-18236 (1999).)
Matriptase is reported to be a protease having activity in degrading extracellular matrix that is localized on the cell surface. When isolated from breast cancer cells (or T-47D cell conditioned medium), matriptase has been reported to be primarily in an uncomplexed form. Matriptase has also been isolated from human milk. When isolated from human milk, matriptase was reported to be in one of two complexed forms, 95 kDa (the predominant form) and 110 kDa; uncomplexed matriptase was not detected. (Liu et al., J. Biol. Chem., 274(26):18237-18242 (1999).) It has been proposed that matriptase exists as an uncomplexed protease when in its active state. In breast milk, matriptase has been reported to exist in complex with a fragment of hepatocyte growth factor inhibitor-1 (HAI-1), a Kunitz-type serine protease inhibitor having activity against trypsin-like serine proteases.
Published PCT application WO 00/53232, “Matriptase, a Serine Protease and Its Applications”, is said to describe matriptase.
Ecotin and Ecotin M84R/M85R have been reported to be macromolecular inhibitors of serine proteases of the chymotrypsin fold and have been reported to inhibit ductal branching, morphogenesis and differentiation of the explanted ductal prostate. PC-3 is a cell line derived from prostate cancer epithelial cells. Ecotin and M84R/M85R ecotin were found to decrease tumor size and metastasis in PC-3 implanted nude mice. Studies to identify additional serine proteases made by cancer cells were done using PC-3 cells. By using PCR techniques and degenerate oligonucleotide primers, five independent serine protease cDNAs were reported isolated from PC-3 mRNA. A serine protease termed “MT-SP1” was cloned, its cDNA characterized and reported to encode a mosaic, transmembrane protease. (Takeuchi et al., PNAS (US), 96:11054-11061 (1999).)
It was subsequently reported that the reported matriptase sequence was included in the translated sequence for the cDNA of MT-SP1. The matriptase cDNA was reported to be a partial MT-SP1 cDNA and to lack 516 of the coding nucleotides (Takeuchi et al., J. Biol. Chem, 275:26333-26342 (2000).) Since the reported matriptase cDNA sequence encoded a possible initiating methionine, it was proposed that alternative splicing could yield a protein lacking the N-terminal region of MT-SP1.
Both matriptase and MT-SP1 are reported to demonstrate trypsin-like protease activity. MT-SP1 has been reported to be a Type II transmembrane protein with an extracellular protease domain. Studies on matriptase have reported that a portion of enzyme molecules were localized on the surfaces of cells.
Additional studies have investigated the substrate specificity of MT-SP1. These experiments have reported that protease-activated receptor 2 (PAR2) and single-chain urokinase-type plasminogen activator (sc-uPA) are macromolecular substrates of MT-SP1. PAR2 is reported to function in inflammation, cytoprotection and/or cell adhesion, while sc-uPa is reported to function in tumor cell invasion and metastasis.
Published PCT application WO 01/57194, “Nucleic Acid Molecules Encoding Transmembrane Serine Proteases, the Encoded Proteins and Methods Based Thereon”, is said to describe polypeptides which comprise protease domains of certain membrane-type serine proteases (“MTSP”), including MTSP1.
Published PCT application WO 99/42120 “TADG-15: An Extracellular Serine Protease Over expressed-in Breast and Ovarian Carcenomas” and U.S. Pat. No. 5,972,616 are said to describe DNA sequences encoding the TADG-15 protein and an isolated TADG-15 protein coded by such DNA sequences.
Published PCT application WO 01/29056 “TADG-15: An Extracellular Serine Protease Over expressed in Carcinomas” is said to describe DNA sequences encoding TADG-15 proteins.
Certain bis-benzamidine compounds which are said to be inhibitors of matriptase were reported by Enyedy et al., J. Med. Chem., 44:1349-1355 (2001).
Published PCT application WO 01/97794 “Structure Based Discovery of Inhibitors of Matriptase for the Treatment of Cancer and Other Conditions”, is said to describe methods of inhibiting carcinoma progression wherein matriptase plays a role and compounds useful in those methods.
Published PCT Application WO 02/08392 “Regulation of Human Matriptase-Like Serine Protease” is said to describe, inter alia, certain matriptase-like serine proteases, methods for their detection, and methods of screening for agents which modulate the activity of a human matriptase-like serine protease.